Influence of ground motion variables on the nonlinear seismic demand of masonry-infilled reinforced concrete frames

Masonry-infilled reinforced concrete (MI-RC) buildings are one of the abundant building inventories and are commonly seen because of their relatively cheaper construction materials, and easier workmanship. However, often due to the negligence of the design guidelines or disregard of the contribution of masonry infills in structural weight and stiffness, these buildings become seismically vulnerable. Generally, the design involves uncertain parameters related to material and geometric properties, a slight change of which may lead to large variation in the structural response. More specifically, the masonry infill wall parameters can result in huge structural response variation. The issue of variation in structural response becomes more critical considering the large uncertainty involved in the quantification of earthquakes and the ground motion parameters while conducting time history analysis. Usually, peak ground acceleration (PGA) is considered as the ground motion intensity measure (IM) to define the ground shaking. However, several other IMs, such as arias intensity, specific energy density, the ratio of peak ground velocity to peak ground acceleration, dominant frequency, and the strong motion duration can also influence and determine the severity of seismic damage caused to the buildings, explicitly in case of infilled RC frames. The present study is an effort to quantify the effect of several such ground motion parameters, on the response of masonry-infilled reinforced concrete frame. An attempt has also been made for modification of the established demand–capacity relationship, also known as IM versus EDP (engineering demand parameter) based on the relative frequency characteristics of the building and the ground motion. It is suggested that relating the EDP with multiple ground motion parameters considering the frequency characteristics of the building and the ground motion can give a more realistic picture of the effect of seismic vibration of such buildings.